Maybe the vils are collecting the mill and the devs just added a "recycling constructions" feature to the game? We're late in real life, and they noticed mankind should've started climate justice back in the age of empires already.
I have already seen that with the new patch some terrains are broken in the scenario editor. Like generating black terrain instead of leaves/cracked sand/water, so maybe the characteristics of the Battle Royale lava terrain have spilled over to another terrain.
If that's the case, we'll be surprised a lot. Is this in the scenario editor or started from single/multiplayer @classicpro?